1. Field of the Invention
The present invention relates generally to a wireless communication system, an electronic price tag system, a wireless communication apparatus, a communication terminal apparatus, and a wireless communication method, and more particularly to a wireless communication system and apparatus for establishing wireless communication between a wireless communication apparatus and a communication terminal apparatus.
2. Description of the Related Art
Generally, at retail stores, price tags are provided on shelves stocking commodities. In recent years and continuing, with the growing competition between rivaling stores, there is an increasing demand for a system for enabling prices of commodities to be flexibly changed. In view of this trend, a so-called electronic price tag system is being developed that is capable of easily reflecting the changes made to prices of commodities on price tags.
The electronic price tag system includes electronic price tags implementing liquid crystal, for example, which are capable of electrically changing their price displays in response to instructions from a computer, for example. In this way, prices of commodities may be flexibly changed and reflected on the price tags. In the electronic price tag system, the electronic price tags do not have to be replaced when prices of commodities are changed. The electronic price tags are battery-driven and are arranged to be capable of establishing data communication for exchanging data pertaining to prices, for example, through wireless communication.
Since the electronic tags are battery-driven, power consumption rate within the electronic tags is preferably minimized, and in this regard, a wireless communication system using infrared light has been proposed in the conventional art. However, in a wireless communication system using infrared light, the wireless communication may be easily hampered by factors such as obstacles and external light.
In turn, a wireless communication system using a radio communication scheme has been proposed, which system is less vulnerable to factors such as obstacles and noise and are capable establishing data communication with accuracy and reliability. Particularly, a wireless communication system using a wireless communication scheme such as that conforming to the IEEE802.15.1 standard or the IEEE802.15.4 standard is being widely contemplated.
FIG.1 is a diagram illustrating a data communication operation using a radio communication scheme according to the prior art.
According to a communication scheme conforming to the IEEE802.15.1 or IEEE802.15.4 standard, a data request and a data response are periodically exchanged at predetermined time intervals. In such an arrangement, in order to reduce power consumption, a communication IC for realizing the communication scheme may be set to sleep mode during the time in which communication is not being established, and the communication IC may be set to data mode only when a data request and a data response are being exchanged (i.e., when data communication is established). However, in such a case, a data request and a data response still have to be exchanged at predetermined time intervals, and thereby, as is shown in FIG. 1, a communication apparatus is switched between sleep mode and data mode several times per second.
It is noted that the power consumption level during data communication may reach up to several dozen mA. However, the price of a commodity at a store may only be changed a few times within one day. In other words, in the above-described arrangement, a communication apparatus is switched between sleep mode and data mode several times per second even though actual data communication is rarely conducted, and thereby, a large amount of power is wasted. As a result, the service life of a battery of an electronic price tag is needlessly reduced.